Abnormal DNA methylation of the Oct-4 enhancer region in cloned mouse embryos.
Oct-4 is essential for normal embryonic development, and abnormal Oct-4 expression in cloned embryos contributes to cloning inefficiency. However, the causes of abnormal Oct-4 expression in cloned embryos are not well understood. As DNA methylation in regulatory regions is known to control transcriptional activity, we investigated the methylation status of three transcriptional regulatory regions of the Oct-4 gene in cloned mouse embryos--the distal enhancer (DE), the proximal enhancer (PE), and the promoter regions. We also investigated the level of Oct-4 gene expression in cloned embryos. Immunochemistry revealed that 85% of cloned blastocysts expressed Oct-4 in both trophectoderm and inner cell mass cells. DNA methylation analysis revealed that the PE region methylation was greater in cloned morulae than in normal morulae. However, the same region was less methylated in cloned blastocysts than in normal blastocysts. We found abnormal expression of de novo methyltransferase 3b in cloned blastocysts. These results indicate that cloned embryos have aberrant DNA methylation in the CpG sites of the PE region of Oct-4, and this may contribute directly to abnormal expression of this gene in cloned embryos.
Kawasumi
Miyuri
M
Division of Biological Science, Graduate School of Biology-Oriented Science and Technology, Kinki University, Wakayama, Japan.
Unno
Yuichi
Y
Matsuoka
Toshiki
T
Nishiwaki
Megumi
M
Anzai
Masayuki
M
Amano
Tomoko
T
Mitani
Tasuku
T
Kato
Hiromi
H
Saeki
Kazuhiro
K
Hosoi
Yoshihiko
Y
Iritani
Akira
A
Kishigami
Satoshi
S
Matsumoto
Kazuya
K
D000818:Animals; D001755:Blastocyst / Q000502:physiology; D019976:Cloning, Organism; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004622:Embryo, Mammalian / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D005260:Female; D005307:Fertilization in Vitro; D018507:Gene Expression Regulation, Developmental; D008297:Male; D051379:Mice; D053652:Nuclear Transfer Techniques; D050814:Octamer Transcription Factor-3 / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D000097584:DNA Methyltransferase 3B
D004248:DNA (Cytosine-5-)-Methyltransferases; D050814:Octamer Transcription Factor-3; D000097584:DNA Methyltransferase 3B